Anesthesia are induced with propofol (2mg/kg) and followed by administering rocuronium 0.6 mg/kg. After tracheal intubation, the lungs of the patients were then ventilated with oxygen in air (1:2) using a tidal volume of 8-10 mL/kg and a respiratory rate of 10-12/min, and the ventilation rate was adjusted to maintain the end-tidal carbon dioxide partial pressure between 35 and 40 mmHg and peak inspiratory pressure below 30 cmH2O. Anesthesia is maintained with desflurane in addition to the continuous infusion of remifentanil. Radial arterial cannulation is done for invasive arterial blood pressure monitoring.